Intra-blood-brain-barrier synthesis of HTLV-III-specific IgG in patients with neurologic symptoms associated with AIDS or AIDS-related complex

IgG intrathecal synthesis in HIV-associated neurocognitive disorder (HAND) according to the HIV-1 subtypes and pattern of HIV RNA in CNS and plasma compartments

We hypothesized that humoral immunity stimulation in the CNS in HIV-1C patients would be lower than that in HIV-1B due to a defective Tat chemokine dimotif (C30C31) that might influence cellular trafficking and CNS inflammation. Sixty-eight paired CSF and blood samples from people with HIV (PWH), free of CNS opportunistic infections, were included, HIV-1B (n = 27), HIV-1C (n = 26), and HIV negative (n = 25). IgG intrathecal synthesis was assayed using quantitative and qualitative methods. IgG oligoclonal bands (OCB) in CSF were observed in 51% of PWH, comparable between HIV-1B and HIV-1C, as well as the medians of IgG intrathecal synthesis formulas. The group with HIV infection aviremic in CSF and blood showed 75% of OCB. There was a poor positive correlation between the IgG quotient and GDS. The impact of HIV-1 on IgG intrathecal production was not subtype dependent. Low-grade CNS intrathecal IgG production persists in HIV CNS infection even in PWH with CSF and blood HIV RNA controlled.

In vitro models of HIV-1 infection of the Central Nervous System

Neurocognitive disorders associated with HIV-1 infection affect more than half of persons living with HIV (PLWH) under retroviral therapy. Understanding the molecular mechanisms and the complex cellular network communication underlying neurological dysfunction is critical for the development of an effective therapy. As with other neurological disorders, challenges to studying HIV infection of the brain include limited access to clinical samples and proper reproducibility of the complexity of brain networks in cellular and animal models. This review focuses on cellular models used to investigate various aspects of neurological dysfunction associated with HIV infection.

Mass Spectrometry Imaging Demonstrates the Regional Brain Distribution Patterns of Three First-Line Antiretroviral Drugs

HIV in the central nervous system (CNS) contributes to the development of HIV-associated neurological disorders (HAND), even with chronic antiretroviral therapy. In order for antiretroviral therapy to be effective in protecting the CNS, these drugs should have the ability to localize in brain areas known to be affected by HIV. Consequently, this study aimed to investigate the localization patterns of three first-line antiretroviral drugs, namely, efavirenz, tenofovir, and emtricitabine, in the rat brain. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) were utilized to assess the pharmacokinetics and brain spatial distribution of the three drugs. Each drug was administered (50 mg/kg) to healthy female Sprague-Dawley rats via intraperitoneal administration. LC-MS/MS results showed that all three drugs could be delivered into the brain, although they varied in blood-brain barrier permeability. MALDI-MSI showed a high degree of efavirenz localization across the entire brain, while tenofovir localized mainly in the cortex. Emtricitabine distributed heterogeneously mainly in the thalamus, corpus callosum, and hypothalamus. This study showed that efavirenz, tenofovir, and emtricitabine might be a potential drug combination antiretroviral therapy for CNS protection against HAND.

Compartmentalized intrathecal immunoglobulin synthesis during HIV infection - a model of chronic CNS inflammation?

HIV infects the central nervous system (CNS) during primary infection and persists in resident macrophages. CNS infection initiates a strong local immune response that fails to control the virus but is responsible for by-stander lesions involved in neurocognitive disorders. Although highly active anti-retroviral therapy now offers an almost complete control of CNS viral proliferation, low-grade CNS inflammation persists. This review focuses on HIV-induced intrathecal immunoglobulin (Ig) synthesis. Intrathecal Ig synthesis early occurs in more than three-quarters of patients in response to viral infection of the CNS and persists throughout the course of the disease. Viral antigens are targeted but this specific response accounts for <5% of the whole intrathecal synthesis. Although the nature and mechanisms leading to non-specific synthesis are unknown, this prominent proportion is comparable to that observed in various CNS viral infections. Cerebrospinal fluid-floating antibody-secreting cells account for a minority of the whole synthesis, which mainly takes place in perivascular inflammatory infiltrates of the CNS parenchyma. B-cell traffic and lineage across the blood-brain-barrier have not yet been described. We review common technical pitfalls and update the pending questions in the field. Moreover, since HIV infection is associated with an intrathecal chronic oligoclonal (and mostly non-specific) Ig synthesis and associates with low-grade axonal lesions, this could be an interesting model of the chronic intrathecal synthesis occurring during multiple sclerosis.

Induction of innate immune responses by SIV in vivo and in vitro: differential expression and function of RIG-I and MDA5

Interferon-β induction occurs during acute simian immunodeficiency virus (SIV) infection in the brain. We have examined expression and function of cytosolic RNA sensors, retinoic acid inducible gene I (RIG-I), and melanoma differentiation-associated protein 5 (MDA5), in vivo in the brain of our consistent, accelerated SIV-macaque model and in vitro in SIV-infected macaque macrophages to identify the pathway of type I interferon (IFN) induction. MDA5 messenger RNA (mRNA) and protein were expressed at higher levels in the brain than RIG-I, with protein expression correlating with the severity of disease from 42 until 84 days post-inoculation. The siRNA experiments reveal that mRNA expression of IFN-inducible gene MxA is dependent on MDA5, but not RIG-I. Finally, we demonstrate that SIV infection leads to the production of double-stranded RNA in vivo, which may act as the MDA5 ligand. We have shown for the first time to our knowledge the functional role of MDA5 in the innate immune response to SIV infection.

Treatment intensification has no effect on the HIV-1 central nervous system infection in patients on suppressive antiretroviral therapy

BACKGROUND

Antiretroviral treatment (ART) significantly reduces cerebrospinal fluid (CSF) HIV-1 RNA levels and residual viremia is less frequently found in CSF than in blood. However, persistent intrathecal immunoactivation is common, even after several years of ART. To investigate whether low-level CSF viremia and residual immunoactivation within the central nervous system (CNS) derive from ongoing local viral replication, we conducted a study of treatment intensification in patients on effective ART.

METHODS

Ten patients on ART with plasma HIV RNA <50 copies per milliliter for >18 months were included. Intensification was given for in total 8 weeks: 4 weeks with maraviroc or lopinavir/ritonavir (good CNS penetration), and 4 weeks with enfuvirtide (poor CNS penetration). Lumbar punctures were performed 4 weeks before, at intensification commencement, at switchover after 4 weeks, at the conclusion of, and 4 weeks after the intensification period.

RESULTS

No significant changes in HIV RNA, neopterin, β2-microglobulin, immunoglobulin G index, albumin ratio, and CD4(+) T-cell count were observed, either in CSF or blood, neither before, during, nor after the intensification periods.

CONCLUSIONS

ART intensification did not reduce residual CSF HIV RNA levels or intrathecal immunoactivation in patients on ART. These findings do not support an ongoing viral replication in CNS.

Quantification of cerebrospinal fluid lactic acid in the differential diagnosis between HIV chronic meningitis and opportunistic meningitis

BACKGROUND

Approximately 40% of HIV infected patients have chronic meningitis at various stages during the infection, 59% are asymptomatic. This is a diagnosis of exclusion and a confounding factor in cerebrospinal fluid (CSF) analysis, any other causes of chronic meningitis by opportunistic or co-infection must be ruled out. The aim of this study was to analyze CSF lactic acid (LA) as an adjuvant biomarker in chronic meningitis due to HIV.

METHODS

CSF LA was quantified in 223 CSF samples by the Dimension AR (Dade Behring, Deerfield, IL, USA), distributed into nine groups: 1) HIV positive with an increase in CSF WBCs (n=17); 2) HIV positive with normal CSF (n=20); 3) enterovirus meningitis (n=33); 4) Herpesviridae meningoencephalitis (n=30); 5) fungal meningitis (n=25); 6) tuberculosis (TB) meningitis (n=17); 7) toxoplasmosis (n=18); 8) neurosyphilis (n=6); 9) control group (n=57).

RESULTS

CSF LA (median; IQR) was higher in samples with TB meningitis (5.5; 2.9-7.5 mmol/L) and Cryptococcus neoformans meningitis (3.9; 2.7-5.8 mmol/L) compated with samples with HIV chronic meningitis (1.7; 1.4-1.9 mmol/L) and other groups (p ≤ 0.0001). For the diagnosis of HIV chronic meningitis, using a cut-off of 3.5 mmol/L, CSF LA showed high sensitivity and negative predictive value, although low specificity.

CONCLUSIONS

CSF LA helps to discriminate between C. neoformans or TB meningitis and HIV chronic meningitis: CSF LA can be included with the methods currently used to identify these specific pathogens, though it does not replace them. It is rapid, inexpensive and easy to perform, and can be used in developing countries.

A hitchhiker's guide to the nervous system: the complex journey of viruses and toxins

To reach the central nervous system (CNS), pathogens have to circumvent the wall of tightly sealed endothelial cells that compose the blood-brain barrier. Neuronal projections that connect to peripheral cells and organs are the Achilles heels in CNS isolation. Some viruses and bacterial toxins interact with membrane receptors that are present at nerve terminals to enter the axoplasm. Pathogens can then be mistaken for cargo and recruit trafficking components, allowing them to undergo long-range axonal transport to neuronal cell bodies. In this Review, we highlight the strategies used by pathogens to exploit axonal transport during CNS invasion.

The role of host genetics in the susceptibility for HIV-associated neurocognitive disorders

Despite progress in the treatment of the Human Immunodeficiency virus (HIV), there continues to be a high prevalence of infected individuals who develop neurocognitive deficits and disorders. Our understanding of the potential cause of HIV-associated neurocognitive disorders (HAND) continues to develop on many fronts. Among them is the study of host genetics. Here, we review the most current information regarding the association between host genetics and risk for HIV infection, AIDS, and HAND. We focus on the role of dopamine dysfunction in the etiology of HAND, and propose a number of genetic polymorphisms within genes related to dopaminergic functioning and other neurobiological factors that may confer vulnerability or protection against HAND.

Regulation of topoisomerase II alpha and beta in HIV-1 infected and uninfected neuroblastoma and astrocytoma cells: involvement of distinct nordihydroguaretic acid sensitive inflammatory pathways

The activity of Topoisomerase II alpha and beta isoforms is tightly regulated during different phases of cell cycle. In the present study, the action of anti-inflammatory agents, nordihydroguaretic acid (NDGA) is analyzed in HIV-1 infected CXCR4(+), CCR5(+) and CD4(-) SK-N-SH neuroblastoma, CXCR4(+), CCR5(+) and CD4(-) 1321N1 astrocytoma and CXCR4(+), CCR5(+/-) and CD4(-) GO-G-CCM glioblastoma cell lines. In SK-N-SH and 1321N1 the expression of Topoisomerase II alpha is concomitant with that of LOX-5 and is highly sensitive to NDGA, while the Topoisomerase II beta is expressed along with TNFalpha and exhibits low sensitivity to NDGA, suggesting distinct pathways of regulation for the two isoforms. HIV-1 infection in these cells enhanced the expression of Topo II alpha and beta. Further, the regulation of Topo II beta and TNFalpha in infected and uninfected SK cells is distinctly different. HIV-1 gp120 derived peptides could block HIV-1 mediated inflammation and Topoisomerase II alpha and beta expression, suggesting the viral mediated response. A combination of NDGA, gp-120 derived peptides and AZT has completely blocked the viral replication, suggesting the enhancement of potency of AZT under the suppression of inflammatory response. In contrast, the expression of Topo II alpha and beta was stimulated by NDGA in GO-G-CCM cells showing distinct regulatory pathway in these cells that was resistant to HIV-1 infection. This suggests the requirement of inflammatory response for productive viral infection. In summary, an induction of co-receptor mediated inflammatory response can distinctly enhance regulated expression of the cellular Topo II alpha and beta and promote productive infection in neurons and astrocytes.

Host response and dysfunction in the CNS during chronic simian immunodeficiency virus infection

CNS abnormalities can be detected during chronic human immunodeficiency virus (HIV) infection, before the development of opportunistic infections or other sequelae of immunodeficiency. However, although end-stage dementia caused by HIV has been linked to the presence of infected and activated macrophages and microglia in the brain, the nature of the changes resulting in the motor and cognitive disorders in the chronic stage is unknown. Using simian immunodeficiency virus-infected rhesus monkeys, we sought the molecular basis for CNS dysfunction. In the chronic stable stage, nearly 2 years after infection, all animals had verified CNS functional abnormalities. Both virus and infiltrating lymphocytes (CD8+ T-cells) were found in the brain. Molecular analysis revealed that the expression of several immune response genes was increased, including CCL5, which has pleiotropic effects on neurons as well as immune cells. CCL5 was significantly upregulated throughout the course of infection, and in the chronic phase was present in the infiltrating lymphocytes. We have identified an altered state of the CNS at an important stage of the viral-host interaction, likely arising to protect against the virus but in the long term leading to damaging processes.

Immunotherapeutic relief from persistent infections and amyloid disorders

Persistent infections and amyloid disorders afflict a significant number of people worldwide. It would appear at first glance that the treatment of these afflictions should be entirely unrelated; however, in both cases components of the adaptive immune system have been harnessed in an attempt to provide some therapeutic relief. Given that the ability of a pathogen to establish persistence often depends in part on a shortcoming of the adaptive immune response, it seems logical to devise immunotherapies with the intention of supplementing (or replacing) the insufficient immunologic element. A case in point is an intervention referred as immunocytotherapy, which relies upon the adoptive transfer of pathogen-specific T lymphocytes into a persistently infected host. Remarkably, the adoptively transferred T lymphocytes not only have the capacity to clear the persistent infection, but can also provide the recipient with protection against subsequent rechallenge (i.e., immunologic memory). Treatment of amyloid disorders (e.g., Alzheimer disease, sporadic inclusion-body myositis) with a similar therapeutic approach is complicated by the fact that the aberrant protein accumulations are self-derived. Focusing the adaptive response on these aberrant self-proteins has the potential to result in autoimmune pathology. This review critically evaluates the importance of immunotherapeutic approaches for the treatment of persistent infections and amyloid disorders, and attempts to delineate the interventions that are most likely to succeed in an exceedingly complex disorder such as sporadic inclusion-body myositis.

Effects of antiretroviral treatment on blood-brain barrier integrity and intrathecal immunoglobulin production in neuroasymptomatic HIV-1-infected patients

OBJECTIVES

To study the effect of antiretroviral combination therapy on blood-brain barrier (BBB) integrity and intrathecal immunoglobulin G (IgG) production.

METHODS

Lumbar punctures were performed on 38 neurologically asymptomatic, treatment-naive HIV-1-infected patients prior to and during treatment at intervals of approximately 4 months, 1 year and 2 years. Albumin ratio and IgG index were analysed as markers of BBB integrity and intrathecal IgG synthesis.

RESULTS

HIV-1 RNA decreased to < 50 HIV-1 RNA copies/mL in the cerebrospinal fluid (CSF) of all patients and in the plasma of all but one patient. Only 5% of patients had elevated albumin ratio values at baseline, while 56% had an elevated IgG index. There was no significant reduction of the albumin ratio or the IgG index. After 2 years of treatment all patients had normal albumin ratio values, while 41% still had increased IgG index levels.

CONCLUSIONS

Up to 2 years after the initiation of treatment, the favourable impact of antiretroviral combination treatment on CSF viral load was not accompanied by a similar reduction of intrathecal IgG production. BBB function, measured as the albumin ratio, was not significantly changed in this cohort of neurologically asymptomatic HIV-1-infected patients.

Influence of depressed mood on neuropsychologic performance in HIV-seropositive drug users

Some studies point out that depression affects the performance of HIV patients in neuropsychological tasks, but at present this effect is not clear. The purpose of the present paper was to study whether the presence of symptoms of depression affects the neuropsychologic performance of seropositive drug users in tasks of attention/concentration, learning and memory, language, construction and visuospatial function, speed of motor performance, cognitive flexibility, manual skill and concept formation and reasoning. In order to carry out this research a sample consisting of 127 male volunteer subjects was used. These subjects were distributed in four groups: one group consisted of HIV-seropositive drug users with symptoms of depression (n = 33); the second group consisted of HIV-seropositive drug users without symptoms of depression (n = 47); the third group was formed by HIV-seronegative drug users with symptoms of depression (n = 15) and the fourth group was formed by HIV-seronegative drug users without symptoms of depression (n = 32). The results reveal the effect of symptoms of depression (evaluated by the Beck Depression Inventory) on the neuropsychologic performance of seropositive drug users. This effect, however, was not observed in the seronegative group. These findings lead us to suggest that symptoms of depression constitute a risk factor for presenting neuropsychologic disturbances in seropositive subjects, which could well be acting as a factor that foments the neuropsychological effects of HIV.

Autoimmune markers in HIV-associated dementia

The etiology of HIV-associated dementia (HAD) is still unknown although direct viral effects have not been supported. Although evidence supports a role for products of activated macrophages, other evidence suggested the possibility of associated autoimmune phenomena at least as a marker. In a blinded analysis, non-HIV-infected whole brain material was immunoblotted with samples of serum, and in certain cases cerebrospinal fluid (CSF), from HAD patients and controls. Distinct antibrain antibodies were detected in 11/12 of HIV+ HAD patients, 7/19 of HIV+ patients without HAD, and 0/11 HIV seronegative controls who were either healthy or had other neurologic diseases. Reactivity against control tissue was negative. Though the etiopathogenetic relation of these antibrain antibodies remains to be delineated, the data suggest that they may be a marker of HAD.

Neuroimmune and neurovirological aspects of human immunodeficiency virus infection

Like most lentiviruses, HIV-1 causes both immune suppression and neurological disease. Neurological disease may occur at any stage of HIV infection but is most apparent with severe immune suppression. Cognitive impairment, reflected strikingly by HIV-associated dementia, has attracted intense interest since the outset of the HIV epidemic, and understanding of its pathogenesis has been spurred on by the emergence of several hypotheses outlining potential pathogenic mechanisms. The release of inflammatory molecules by HIV-infected microglia and macrophages and the concurrent neuronal damage play central roles in the conceptualization of HIV neuropathogenesis. Many inflammatory molecules appear to contribute to the pathogenic cascade and their individual roles remain undefined. At the same time, the abundance of virus in the brain and the type or strain of virus found in the brain may also be important codeterminants of neurological disease, as shown for other neurotropic viruses. Coreceptor use by HIV found in the brain appears to closely mirror what has been reported in systemic macrophages. The impact of HAART on viral genotype and phenotype found in the brain, and its relationship to clinical disease, remain uncertain. Several interesting animal models have been developed, using other lentiviruses, transgenic animals, and HIV-infected SCID mice, that may prove useful in future pathogenesis and therapeutic studies. Despite the progress in the understanding of HIV neuropathogenesis, many questions remain unanswered.

Assessment of HIV-intrathecal humoral immune response in AIDS-related neurological disorders

Intrathecal synthesis of IgG directed to HIV antigens was investigated by antibody specific index (ASI), affinity-mediated immunoblot (AMI) and Western blot (WB) assay in a group of 88 AIDS patients of which 28 with HIV-associated neurological disorders (HAND), 13 without associated neurological disorders (WAND) and 47 with non-HIV-associated neurological disorders (non-HAND). CD4+ count was above 50 cells/mm3 (CD4+>50) in 30 and below 50/mm3 (CD4+<50) in 58 patients, respectively. A significantly higher frequency for CSF complete anti-gag profile (p<0.001), and for HIV-specific oligoclonal patterns ("mixed" pattern=p<0.01) was observed in HAND as compared to patterns from the other clinical groups. A decrease in complete anti-env, anti-pol and anti-gag reactivity was present in CSF of patients with CD4+<50 as compared to those with CD4+>50. Our findings suggest that AIDS appears to be characterized by an anti-HIV intrathecal humoral immune response which is principally directed to env products with a prevalence of oligoclonal patterns and CSF complete anti-gag profile in HIV-associated neurological involvement.

Microglia in HIV-associated neurological diseases

Human immunodeficiency virus type-1 (HIV-1) is a neurotropic virus linked to a variety of progressive neurologic disorders. This review describes our current understanding of how HIV-1 enters the nervous system and interacts with neuronal and non-neuronal cells to initiate and sustain neurologic dysfunction. The overwhelming majority of cells infected with HIV-1 in the nervous system are microglia/macrophages. Microglial/macrophage infection leads to immune dysregulation as well as production and release of cytotoxic molecules. Interaction of these infected cells with astrocytes may accelerate neurotoxic mechanisms. A hypothetical scenario for how HIV-1 infection leads to neurologic disease is presented.

Investigation of distribution, transport and uptake of anti-HIV drugs to the central nervous system

The distribution of currently available anti-HIV drugs into the CNS is reviewed with a focus on transport mechanisms. Among these drugs, nucleoside analogs are most well studied for their CNS distribution. The average reported values of the CSF/plasma steady-state concentration or corresponding AUC ratios are 0.23 (AZT), 0.06 (ddI), 0.04 (ddC), 0.49 (d4T), and 0.08 (3TC). Active efflux transport out of the CNS appears to be a predominant mechanism limiting nucleoside access to the CNS, although poor penetration may contribute to some extent for some polar nucleosides. The nature of the efflux pump for these drugs is speculated to be MRP-like transporter(s) in blood-brain and blood-CSF barriers. For non-nucleoside and protease inhibitors, much research remains to be done on the extent, time course, and mechanisms of their CNS distribution. The CNS penetration of some protease inhibitors is restricted by P-glycoprotein. A better understanding of transport mechanisms of anti-HIV drugs in the CNS is essential to develop approaches to enhance CNS delivery of available drugs and to identify new drugs less subject to active efflux transporter(s) in the CNS.

Protective role of the virus-specific immune response for development of severe neurologic signs in simian immunodeficiency virus-infected macaques

The pathogenesis of human immunodeficiency virus-associated motor and cognitive disorders is poorly understood. In this context both a protective and a harmful role of the immune system has been discussed. This question was addressed in the present study by correlating the occurrence of neurologic disease in simian immunodeficiency virus (SIV)-infected macaques with disease progression and the humoral and cellular intrathecal antiviral immune response. Overt neurologic signs consisting of ataxia and apathy were observed at a much higher frequency in rapid progressor animals (6 of 12) than in slow progressors (1 of 7). Whereas slow progressors mounted a strong antiviral antibody (Ab) response as evidenced by enzyme-linked immunosorbent and immunospot assays, neither virus-specific Ab titers nor Ab-secreting cells could be found in the cerebrospinal fluid (CSF) or brain parenchyma of rapid progressors. Similarly, increased infiltration of CD8(+) T cells and cytotoxic T lymphocytes specific for viral antigens were detected only in the CSF of slow progressors. The finding that neurologic signs develop frequently in SIV-infected macaques in the absence of an antiviral immune response demonstrates that the immune system does not contribute to the development of motor disorders in these animals. Moreover, the lower incidence of neurologic symptoms in slow progressors with a strong intrathecal immune response suggests a protective role of the virus-specific immunity in immunodeficiency virus-induced central nervous system disease.

Advanced laboratory techniques for diagnosing Toxoplasma gondii encephalitis in AIDS patients: significance of intrathecal production and comparison with PCR and ECL-western blotting

The polymerase chain reaction (PCR) for detection of cerebral spinal fluid (CSF) Toxoplasma gondii DNA was combined with the study of intrathecal antibody synthesis by antibody specific index calculation (ASI) and the detection of specific oligoclonal IgG bands (OCB) by affinity mediated immunoblotting (AMI) in 11 AIDS patients with T. gondii encephalitis (TE) and in 20 control patients with or without neurological disorders. Enhanced chemiluminescence (ECL) western-blot technique was employed to evaluate the antigenic specificity of CSF-IgG towards individual T. gondii antigens. PCR was positive in all TE patients which displayed brain-derived or blood-derived specific OCB, even when comparative ASI failed. Four TE patients had a unique anti-T. gondii OCB restricted to the CSF and a strong antibody response toward the 29 kDa band by ECL western blot. This response could be an important marker to discriminate TE from other opportunistic central nervous system (CNS) infections in the course of AIDS.

The effects of human immunodeficiency virus in the central nervous system

More than a decade after the first description of HIV DNA in the nervous system the pathophysiology of HIVD remains largely enigmatic, with data supporting a number of potential mechanisms for the development of neuronal dysfunction. Nevertheless, a few key findings have considerable support in the literature devoted to this subject: 1. HIV dementia is caused by HIV itself; no other pathogen has been consistently found in the brains of patients with HIVD. 2. In comparison with other viral encephalopathies, there appears to be a significant discordance between the amount of virus being produced in the brains of patients with HIVD and the degree of neurological deterioration. 3. The key cell types responsible for viral production within the CNS are the resident macrophages or microglial cells. 4. Other elements within the CNS, particularly astrocytes, are probably infected with HIV as well, but all of these infections are highly restricted in terms of production of virus or viral structural proteins. 5. At least one component of the pathogenesis of HIVD may be the generation of neurotoxins by infected microglia, although the type of neurotoxin, and the specific compound most likely to be involved, are quite controversial. Advances with combination antiviral therapy have successfully reduced plasma viral load in a high proportion of individuals, leading to the speculation (previously almost heretical) that it may be possible to eradicate HIV completely from the systemic immune system. If that were the case, potential "sanctuary" sites such as the immunologically protected CNS might remain as important reservoirs for reseeding of lymphoid tissues. Microglia may be particularly suited for this purpose because they are long lived, can produce HIV for several weeks (at least in culture), and they are apparently relatively immune to virus-induced cytopathology such as syncytium formation. One can speculate about several scenarios resulting from the continued presence of replication-competent HIV within brain. In the worst case, a smoldering infection of the nervous system could lead to neurological deterioration without reinfection of systemic immune cells. The epidemiological data indicating that HIVD is a disease primarily associated with immunodeficiency suggest that the systemic immune system plays a role in maintaining virus residing within the CNS under control. Thus it is quite possible that this scenario would not occur for many years after the systemic infection is controlled. Alternatively, virus could be transported from the CNS by circulating lymphocytes and monocytes and reinfect systemic organs. This would necessitate restarting therapy for those individuals who were previously thought to be cured, but presumably virus within the CNS would not have developed resistance to antivirals. In either case, the techniques currently available do not permit an accurate assessment of CNS HIV load in living people, and this question will remain unanswered until antivirals are discontinued in a few individuals with persistently negative tests for systemic virus. In addition to this most critical question, the relationship between viral levels and HIVD is largely unexplored, as is the possibility that some strains are particularly virulent or neuroinvasive. Furthermore, the potential contribution of host genotype in the development of dementia is unknown. In view of the strong influence of major chemokine receptor (CCR5) truncations on HIV replication, it is entirely possible that more discrete genetic polymorphisms have a subtle effect on either brain invasion or virulence.

Relationship between human immunodeficiency virus-associated dementia and viral load in cerebrospinal fluid and brain

Cerebrospinal fluid (CSF) human immunodeficiency virus (HIV) RNA levels were measured with the Nucleic Acid Sequence-Based Amplification (NASBA) assay to determine the relationship with neurological status; 37 subjects with HIV dementia (HIV-D) were compared with 77 with HIV with minor neurological signs (HIV-MCMD) and 93 neurologically normal HIV-seropositive individuals (HIV-NML). The NASBA assay had a lower limit of detection of 100 copies per milliliter. Mean CSF log HIV RNA levels were significantly higher in those with dementia after adjusting for CD4 count and were correlated with dementia severity. Plasma levels did not distinguish comparably immunosuppressed subjects with or without dementia. CSF and plasma RNA levels were significantly intercorrelated for subjects with CD4 counts <200/mm3 and also correlated inversely with CSF beta2-microglobulin. CSF RNA levels were independent of CSF pleocytosis or antiretroviral exposure. Brain RNA levels were consistently higher than CSF but correlated with CSF values for dementia subjects. The NASBA assay can be used reliably to determine HIV RNA levels in CSF, brain, and plasma samples. CSF HIV RNA may be a surrogate marker for brain infection, based on the observed correlation with brain levels. The association between plasma HIV RNA and CSF levels of HIV and beta2-microglobulin suggests that both viral load and CNS immune activation are important determinants of neurological disease.

Antigen-specific oligoclonal IgG in AIDS-related cytomegalovirus and toxoplasma encephalitis

We retrospectively studied serum and cerebrospinal fluid (CSF) specimens from AIDS patients with either Cytomegalovirus (2 cases) or Toxoplasma gondii (5 cases) encephalitis. The samples, which had previously proved to be negative for total IgG oligoclonal bands (OCBs), were investigated for antigen-specific OCBs directed to the disease-related opportunistic agent.

MATERIAL & METHODS

Paired serum and CSF samples from the given AIDS patients were considered. We undertook affinity immunoblotting of either virus- or protozoan-specific IgG onto antigen-coated nitrocellulose paper after protein separation by agarose isoelectric focusing (IEF).

RESULTS

Antigen-specific OCBs to the disease-related opportunistic agent were detected in serum and in CSF samples from all the patients.

CONCLUSIONS

During overt AIDS, routine IEF methods may fail to detect OCBs, probably because nonspecific polyclonal hypergammaglobulinemia, which is typical of this disease, reduces their visibility. Our IEF/immunoblotting profiles are characterized by identical serum and CSF bands. The detection of antigen-specific OCBs may support the diagnosis of some opportunistic infections of the central nervous system in AIDS.

A novel approach to the determination and characterization of HIV dementia

BACKGROUND

Neuropsychological studies of the pattern and extent of cognitive impairment in HIV-infected patients have mostly used deviations from control values and/or cut-off scores as criteria for classification of dementia. There is, however, no agreement as to how to define impairment, and classification is imprecise.

METHOD

The current study used a dementia classification matrix, developed with a step-wise linear discriminant analysis of neuropsychological data from patients with primary neurodegenerative dementias, to classify symptomatic HIV patients as demented or non-demented, and further to differentiate cortical and subcortical dementia patterns. Thirty-two male and 2 female patients (mean age 39 +/- 2) with symptomatic HIV disease (mean absolute CD4 count 195 +/- 41) participated in the study.

RESULTS

Thirty-five per cent of patients were classified as demented. Of these, 83% showed a subcortical pattern and 17% a cortical profile of deficits. Significant differences between patients classified as subcortically demented and those categorized as normal on neuropsychological measures associated with subcortical integrity further validated the classification. Measures of psychiatric status between subgroups were similar.

CONCLUSION

Since certain treatments may delay or reverse cognitive deficits, the use of an objective classification method based on discriminant analysis may help to identify patients who may benefit from therapy.

High levels of anti-HIV-1 envelope antibodies in cerebrospinal fluid as compared to serum from patients with AIDS dementia complex

The antibody response to the HIV-1 envelope protein has not been well characterized in patients with AIDS dementia complex (ADC). We evaluated the frequency of antibodies against the HIV-1 envelope in cerebrospinal fluid (CSF) and serum from 21 persons with ADC and 10 symptom-free HIV-1-positive subjects using Western immunoblot with reducing and nonreducing buffer and radioimmunoprecipitation (RIP) analysis. RIP analysis revealed anti-envelope antibodies in all sera tested. Higher anti-envelope levels were observed in CSF than in serum of 12 of 21 ADC patients and only 1 of 10 symptom-free subjects (two-sided Fisher exact test, p < 0.05). All persons with moderate to severe ADC had higher anti-envelope levels in CSF than in sera (p < 0.005). CSF anti-gp120 antibodies were not as readily detected by Western blot analysis even under nonreduced conditions, suggesting that they are directed to conformational epitopes. Higher CSF anti-envelope antibodies appear to be more common in patients with ADC than in symptom-free HIV-1-positive subjects. This antibody pattern may serve as a marker for ADC and its progression.

Neuroepidemiology of HIV infection

There are a variety of HIV-related neurologic complications that have numerous causes. HIV-related neurologic illnesses are specific to the stage of HIV infection, although the greatest burden of neurologic disease and the most disabling syndromes occur in the more advanced stages. As the number of HIV-infected persons continues to increase worldwide and as antiretroviral and other anti-infective therapies improve patient survival in the advanced stages of HIV infection, the burden of neurologic disease will continue to increase.

Lymphoid cell resistance to glucocorticoids in HIV infection

In humans infected with the HIV-1 virus there may be a disproportionate severity of signs and symptoms of illness compared to the fraction of CD4+ infected T-lymphoid cells. In part, this may be due to altered intercellular signalling systems and intracellular signal transduction. Glucocorticoids are well known for their effects on the vitality and function of lymphoid cells. Patients with HIV infections often show elevated circulating levels of cortisol, suggesting some misfunction in the regulatory systems that maintain the levels of this critical hormone. At the cellular level, it is known that both acute HIV infection and glucocorticoids can cause apoptotic cell death in thymic lymphocytes. However, chronically HIV-infected cells appear to be resistant to glucocorticoid-evoked cell death. Glucocorticoid receptor-ligand binding studies on patients' cells have shown reduced affinity between the receptor binding sites and test steroids. In vitro, chronically HIV-infected cells of the lymphoid CEM line displayed resistance to glucocorticoid-induced apoptosis. These cells showed reduced numbers of binding sites with little alteration in apparent affinity between ligand and receptor. Thus it appears that there may often be malfunction of the normal glucocorticoid response in HIV-infected cells probably due to altered interactions between the glucocorticoid receptor and its hormone. Such alterations may have clinical consequences, including the possibility of a relatively longer life span of infected CD4+ T-lymphocytes, as well as systemic effects of chronically elevated cortisol level.

Absence of serological evidence for foamy virus infection in patients with amyotrophic lateral sclerosis

Foamy virus (FV) infection has been implicated in the pathogenesis of sporadic motor neuron disease (MND) by means of serological assays. To confirm these results we tested serum and cerebrospinal fluid (CSF) samples from 23 cases of clinically verified non-familial MND and 11 cases of suspected non-familial MND for the presence of FV infection as determined by Western blot (WB) and indirect immunofluorescence assay (IFA). Using the same tests we also screened sera from 87 healthy chimpanzees for the presence of FV antibodies. None of the human samples in question tested positive. However, the testing revealed that 84 of 87 chimpanzees (96.6%) were seropositive for FV, indicating that combined WB and IFA are suitable methods for the serodiagnosis of FV infection. Given these results an association of FV infection and sporadic MND is highly improbable. Furthermore a suggested therapeutic trial with anti-retroviral drugs appears unjustified.

Cerebrospinal fluid antiganglioside antibodies in patients with AIDS

In this study the presence of brain antiganglioside antibodies in the cerebrospinal fluid (CSF) of patients with HIV infection was analysed. CSF samples were collected from 45 patients with AIDS and from 45 anti-HIV negative subjects, 15 of whom presented aseptic meningitis. Nineteen AIDS patients had clinically well-documented encephalopathy. Thirteen of these patients had white matter lesions shown by magnetic resonance imaging (MRI). Both IgG and IgM antiganglioside antibodies were detected by immunostaining on thin layer chromatography plates in three CSF samples from AIDS patients with progressive encephalopathy with signs of a diffuse demyelination, as revealed by MRI. Two of these CSF samples reacted specifically with GM3, GM1 and GD1a and one with GD1a. In none of the HIV infected patients without demyelinating encephalopathy, but with opportunistic infections or cerebral lymphoma, nor in the anti-HIV negative control subjects were antiganglioside antibodies detected. No association with JCV DNA, CMV DNA, EBV DNA, detected by nested PCR, nor HIV antigen p24 was found. These findings show the presence of brain antiganglioside antibodies in the CSF of AIDS patients for the first time. However, the findings do not suggest relating the presence of these antibodies to HIV encephalopathy or particular viral agents, but indicate that the antibodies are detectable in subjects with progressive encephalopathy with a diffuse demyelination.

AIDS-related optic neuropathy: a histological, virological and ultrastructural study

BACKGROUND

Clinical and histopathological evidence of optic nerve axonal loss has been reported in AIDS patients without retinitis. The study was carried out to investigate the possible involvement of HIV-infected cells in the development of optic nerve degeneration.

METHODS

Optic nerves were obtained from eight AIDS patients and four normal controls. These nerves were morphologically and immunohistochemically analyzed. Additionally, using PCR amplification techniques, the retina and optic nerve samples obtained from three HIV-seropositive patients and one control were examined for the presence of HIV and cytomegalovirus antigens.

RESULTS

We noted various stages of axonal degeneration in the optic nerves obtained from AIDS patients in whom there was an absence of retinal findings. Characteristic glial changes involving hypertrophic astrocytes, vacuolated oligodendrocytes, and mononuclear phagocyte series cells were also seen in the AIDS optic nerves. HIV DNA was present in at least four of five optic nerves but in only one of five retinas. Control specimens were each negative for all cytomegalovirus and HIV antigens.

CONCLUSIONS

Degeneration in the optic nerve may be mediated by HIV-infected macrophages rather than by direct viral infection of neurons. Axonal degeneration due to AIDS at the level of the optic nerve can occur independently of retinal infection.

HIV-1 heterogeneity and cytokines. Neuropathogenesis

Mild manifestations (HIV-1 associated minor cognitive/motor disorder), severe manifestations (HIV-1 associated dementia complex and HIV-1 associated myelopathy), and sensory neuropathy are consequences of HIV-1 infection. Our goal is to elucidate the role of HIV-1 in the complications of AIDS including cytokine immunopathology and HIV-1 DNA sequence variants. We have examined the brain and sensory ganglia from 60 AIDS patients and 20 seronegative controls using PCR, DNA sequencing of the HIV-1 envelope protein (env), in situ hybridization (ISH), and immunohistochemistry (IHC). Using our combined ISH-IHC technique, we could identify different types of cells and HIV-1 simultaneously in cryostat and paraffin sections. We found HIV-1 predominantly in macrophage/microglia in brain. In dorsal root ganglia (DRG) we found rare macrophages infected with HIV-1 and neurons and interstitial cells (including macrophages) which were apoptotic. Cytokines were detected in mononuclear and endothelial cells near neurons. We achieved single copy sensitivity detecting HIV-1 in nervous tissue using nested PCR. We sequenced HIV-1, DNA from 3 intravenous drug users (IDUs): from brain, CSF, and blood. PCR amplification was followed by cloning and then sequencing the HIV-1 insert: V1-V5 regions of the envelope (env) gene. We found that the env genes had increased sequence variation compared to the literature, cDNA sequences derived from RNA were less heterogeneous than clones derived from DNA from the same specimens, clones derived from brain are more closely related (show restricted heterogeneity) compared to clones from blood and CSF from the same patients. Patient 149 clones we examined to date did not correspond to any of the designated subtypes (A-F) of HIV-1 based on the DNA sequences of the C2-V3 regions. Finally, the HIV-1 RNA produced in these tissues is derived from a minority of DNA clones. Although HIV-1 infected macrophages are not entirely responsible for pathology in the brain and less so in sensory ganglia, some of the products of infection, cytokines, are more widespread in these tissues. Furthermore, HIV-1 strains infecting the brain appear to exhibit restricted heterogeneity compared to autologous CSF and blood and these strains may be associated with cytokines and pathology. HIV-1 strains that infect nervous tissue and cytokines produced in this tissue may effect neuropathogenesis, in vivo, in spite of low levels of local HIV-1 infection. We attempt to delineate, here, common sequence variations in HIV-1 isolates in the hope of developing future therapeutic strategies.

Role of immune activation and cytokine expression in HIV-1-associated neurologic diseases

Central nervous system (CNS) involvement is common during human immunodeficiency virus type-1 (HIV-1) infection. The neurologic disease of the CNS most frequently observed during acquired immunodeficiency syndrome (AIDS) is HIV-1-associated cognitive/motor complex or AIDS dementia complex (ADC), which is most likely a direct consequence of HIV-1 infection of the CNS. The peripheral nervous system (PNS) is also affected in HIV-1-infected individuals and there are several features of immune- and cytokine-related pathogenesis in both the CNS and PNS that are reviewed. Several lines of evidence demonstrate aspects of immune activation in the CNS and peripheral nervous system (PNS) of HIV-1-infected individuals. The relative paucity of HIV-1 expression in contrast to widespread functional and pathologic changes in the CNS and PNS of AIDS patients, and the lack of evidence of productive infection of HIV-1 in neuronal cells in vivo lead to the possibility of indirect or immunopathogenic mechanisms for HIV-1-related neurologic diseases. Proposed mechanisms of neuronal and glial cell damage are injury of oligodendrocytes by tumor necrosis factor-alpha (TNF-alpha) released from activated macrophage/microglia, calcium-dependent excitoneurotoxicity induced by gp120 HIV-1 envelope protein, N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity by quinolinic acid (a product of activated macrophages), cell injury by HIV-1-specific cytotoxic T cells, and apoptosis of oligodendrocytes or neurons triggered by interaction between cell surface receptors and HIV-1 gp120 protein. Common to those mechanisms is the dependence on cellular activation with expression of proinflammatory cytokines (TNF-alpha, interleukin-1). Amplification of activation signals through the cytokine network by macrophage/astrocyte/endothelial cell interactions, and cell-to-cell contact between activated macrophages and neural cells by upregulation of adhesion molecules dramatically enhances the toxic effect of macrophage products. Expression of immunosuppressive cytokines such as interleukin-4, interleukin-6, and transforming growth factor-beta is also increased in the CNS and PNS of HIV-1-infected patients. This may serve as neuroprotective and regenerative mechanism against insults to nervous system tissue.

Anticardiolipin antibodies in HIV infection: association with cerebral perfusion defects as detected by 99mTc-HMPAO SPECT

Anticardiolipin antibodies (ACA) belong to a heterogeneous group of antibodies directed against negatively charged phospholipids. In patients with rheumatic disorders, their presence has been correlated to the occurrence of thromboembolic complications, thrombocytopenia, abortions and other disease manifestations. Several studies have revealed the detection of mostly high-titre ACA in a significant proportion of HIV-infected patients without any known clinical relationship. In our study, ACA were detected in 17/34 HIV-infected patients, and their presence was significantly associated with the detection of cerebral perfusion abnormalities by 99mTc-HMPAO SPECT. SPECT scans were classified as normal or as focal or diffuse defects in uptake. Most patients (13/16) with cerebral perfusion defects had elevated ACA titres in contrast to 4/18 patients with normal SPECT findings (P = 0.002). Focal uptake defects were always associated with the presence of ACA. No correlation to clinical features or other laboratory parameters was evident. Our results suggest a possible implication of autoimmune mechanisms in the pathogenesis of cerebral perfusion abnormalities detected by SPECT scanning in HIV-infected patients. However, further studies are needed to evaluate the clinical significance and to develop possible therapeutic consequences.

Quantitation of intrathecal measles virus IgG antibody synthesis rate: subacute sclerosing panencephalitis and multiple sclerosis

A method for quantitating specific anti-viral antibodies in serum and cerebrospinal fluid (CSF) is established using enzyme-linked immunosorbent assay (ELISA). Quantitated antibody levels are used to determine intrathecal specific IgG synthesis rate for the particular antibody. Measles virus was used as a model for validating this quantitative technique: a mutated form of measles virus is a cause of subacute sclerosing panencephalitis (SSPE) and there is a possibility that measles virus is related to the cause of multiple sclerosis (MS). Matched serum and CSF samples were assayed. Concentration of anti-measles IgG was determined and intrathecal measles-specific IgG synthesis rate was calculated. For the SSPE samples, measles-specific IgG synthesis rate was elevated and comprised > 20% of the total intrathecal IgG synthesis rate; these results are consistent with the literature. The ELISA method can be performed routinely, providing a quick, simple, reproducible means of quantitating specific antibody concentrations, with sensitivity greater than 1 nanogram per milliliter. With this method, quantitation of IgG antibodies to any other viral antigen can be reliably and precisely determined.

Cross-reactivity of anti-human immunodeficiency virus type 1 gp41 antibodies with human astrocytes and astrocytoma cell lines

An antigen expressed by astrocytes in human brain tissue and by various human astrocytoma cell lines was shown to cross-react with a monoclonal antibody generated against amino acids (aa) 584 to 609 of the transmembrane protein gp41 of human immunodeficiency virus type 1 (HIV-1). This region is an immunodominant segment of gp41, and high levels of antibodies against this epitope have been detected in both serum and cerebrospinal fluid of HIV-infected individuals at all stages of HIV infection. Immunohistochemistry with this monoclonal antibody demonstrated the presence of a cross-reactive antigen in human brain tissue, with an increased frequency and intensity of staining in HIV-positive individuals when compared with HIV-negative controls. By using a panel of HIV-positive and -negative sera, we show that antibodies in HIV-positive serum specifically bound to the surfaces of human astrocytoma cells. HIV-positive sera depleted of antibodies recognizing gp41 aa 584 to 609 showed a significant diminution in cell surface binding. Conversely, the serum antibodies that bound to and were eluted from the aa 584 to 609 peptide also bound to the astrocyte cell surface. To identify the target antigen, the immunoreactivity of three astrocytoma cell lines was examined. By immunoprecipitation of metabolically labeled cell lysates and Western blot (immunoblot) analysis, we identified a protein of approximately 100 kDa as the target antigen. Cross-reactive antibodies between HIV proteins and astrocyte epitopes, such as this 100-kDa protein and others previously reported, suggests that an autoimmune response against these target antigens may disrupt the normal functions of astrocytes.

Ophthalmoplegia associated with AIDS

A 34-year-old man with AIDS was admitted to the hospital with a one-week history of cough, chest pain, and fever. Radiography revealed a cavitating left upper lobe lesion. Two weeks later he developed a headache associated with a contrast enhancing lesion in the right parietal lobe. The patient had a progressive downhill course, developing atrioventricular block and hypernatremia. Neuro-ophthalmologically, there was a mild facial droop, "hand motions" vision with presumed bilateral cytomegalic inclusion retinitis, and signs of a mesencephalic syndrome, including lid retraction. Discussions center on the differential diagnosis of the central nervous system disease and the obligative recommendations the neuro-ophthalmologist must be willing to make.

The Soriano Award Lecture. Emerging infections of the nervous system

The epidemic of acquired immunodeficiency disease [AIDS] has focused interest on the origins of "new" infectious agents. Great plagues are well known from the distant past, but a number of novel diseases affecting the nervous system infections have emerged in recent years. The causes of such new disorders are diverse: whereas rapid mutations of microbes allow the evolution of truly novel agents, the appearance of new diseases is more often due to changes in human or vector populations or changes in societal mores that result in dissemination of preexistent microbes. Examples of recently emerging infections that involve the nervous system include the enterovirus 70 epidemics with poliomyelitis-like disease, the appearance of California virus encephalitis in the midwestern United States, the rapid spread of Lyme disease with its many neurological complications in the eastern United States, and the outbreak of bovine spongiform encephalopathy in the United Kingdom, in addition to the devastating epidemic of human immunodeficiency virus (HIV), which will cause nervous system disease in over half of those infected. As the world population increases and modern transportation brings us closer into a "global village" more new agents will emerge and more will be sustained. Knowledge of the molecular biology and ecology of the agents and awareness of how our actions can alter their behavior are our best defense.

HIV-1 infection of the developing nervous system: central role of astrocytes in pathogenesis

Recent studies in our laboratory and that of Dr. Howard Gendelman have revealed two important pathways for neuronal damage during HIV-1 encephalopathy in children. First, substantial numbers of astrocytes are actively or latently infected with HIV-1. Astrocyte infection may lead to neuronal dysfunction through loss of supporting growth factors, excitotoxicity due to dysregulation of neurotransmitter reuptake, and loosening of the blood-brain barrier permitting further seeding of HIV-1 in the CNS. Significantly, infection of astrocytes is marked by near-exclusive synthesis of early regulatory gene products of HIV-1, while structural proteins characteristic of productive infection are found in macrophages, microglia and multinucleated giant cells. We propose the term 'restricted' to denote the non-productive infection found in astrocytes. Second, HIV-1-infected macrophages initiate inflammatory processes which are amplified through cell-cell interactions with astrocytes. Macrophage-astrocyte interactions produce arachidonic metabolites and potentially neurotoxic cytokines (TNF-alpha and IL-1 beta), leading to astroglial activation and proliferation which then amplifies these cellular processes. These new findings suggest that two major pathways leading to neurotoxicity in pediatric AIDS encephalopathy are linked to HIV-1 infection through astrocyte-mediated processes, and help explain how small numbers of productivity infected cells indirectly cause widespread tissue pathology and elicit profound neurological impairment.